The revolution in the understanding of neuromuscular diseases has been founded on careful clinical observation, neurophysiologic technologies, and histopathology. This protocol has been carried out to learn more about established diseases, to characterize new diseases, to assess current methodologies and technologies, and to refine old methods and develop new ones. To date, three patients with sarcoid neuropathy have been evaluated and have been shown to have a distal symmetrical sensory and motor polyneuropathy of axonal type. This is the largest series to date. Five patients with hemifacial spasm have been evaluated and findings indicate that the primary abnormalities may be generated by ectopic excitation and ephaptic transmission of axons in the peripheral facial nerve. These findings corroborate those which have recently been detailed in the literature. In addition, the findings suggest that a similar pathogenesis may be involved in post- paralytic facial abnormalities. Thirty-five patients with diagnostically difficult neuromuscular diseases have been evaluated and nearly fifty percent of them have yielded satisfactory diagnosis. Several of these cases are suitable for clinical reports. All of the findings have directly benefited the patients. Fourteen patients have undergone a critical assessment of the symmetry of the sensory action potentials and preliminary findings indicate that significant asymmetries of sensory action potentials may exist. Twenty-five cases have had direct comparison of near-nerve recording and surface recording techniques and preliminary findings indicate good correlations of the techniques. Four cases of nerve biopsy have been studied with in vitro compound action potentials and this is a useful adjunct technique in the evaluation of nerve biopsies.